I think the biggest challenge people are having with ActivityPub is that they are, for the first time, generally encountering a "structured open world system" for the first time.
Closed world systems let you control (and prove) a lot, but you can only do the things your own "world" has built an idea up about. Also "easier" to build DB schemas for, etc. But hopeless for extensibility when talking with the rest of the world.
Meanwhile, completely free-for-all-json, coordinating on meaning is nigh impossible.
But every computer program is, until we have human equivalent AI, a closed world. You can provide all the metadata you want about the open world, but if my program doesn't already have an idea about it, it can't do anything smarter with it than either ignore it or pretty print it.
I'm not trying to be argumentative as such; I *know* you've put a ton of thought into it. But I absolutely can't grasp where the LD community is coming from.
I haven't officially changed my name yet, but for the sake of paperwork minimization and local friend confusion maximization, I will be switching my middle name to my spouse's last name rather than hyphenating.